The present invention is aimed specifically at remedying these drawbacks, and in particular at providing a process for tracking and/or monitoring the operation of a near-infrared spectrometer and the manufacturing unit to which it is linked.
By virtue of this process it is possible to expose disturbances, drifting, anomalies of operation of the spectrometer and of the associated measurement rig as well as of the manufacturing unit to which it is linked, to identify the causes of these malfunctions and to make provisions suitable for each situation: for example to declare the result of an analysis invalid and to warn the operator running the unit to which the spectrometer is linked and to supply him with elements for making his decisions.
This process finds its application in analysis laboratories and the manufacturing units of the chemical, petroleum, pharmaceutical, cosmetological and agro-food industries.
For this purpose the present invention proposes a process for tracking and monitoring the operation of a unit for manufacturing a product and/or a near-infrared spectrometer fed with the product, the said spectrometer delivering spectra consisting of series of values of absorbance for various values of wavelengths, consisting in executing the following steps:
periodically recording, in the form of numerical data, spectra arising from the near-infrared spectrometer, PA1 mathematically transforming the numerical data of each recorded spectrum so as to obtain transformed spectra, PA1 constructing a string of work spectra from the values previously obtained, by choosing wavelengths in each transformed spectrum, by a method of selection, PA1 selecting from the string of work spectra, a first set of work spectra containing from 20 to 50 consecutive spectra, PA1 selecting from the string of work spectra, a second set of work spectra, of the same dimension as the first set, the spectra being consecutive and shifted in time with respect to the spectra of the first set, PA1 computing at least one quality criterion so as to intercompare the first and second sets of spectra, PA1 tracking the evolution of the quality criterion over time.
characterized in that it consists in executing the following steps also:
According to another characteristic of the invention, the method of selection of the wavelengths of the work spectra is chosen from among the method of stepwise selection, the method of selection by elimination, a method applying a regression algorithm and a method implementing genetic algorithms.
According to another characteristic of the invention, the first set of work spectra comprises spectra obtained from reference products with known characteristics.
According to another characteristic of the invention, the first set of work spectra containing a first spectrum, the second set of work spectra consists of the same spectra as the first set, except for the first which is replaced with a spectrum not belonging to the first set.
According to another characteristic of the invention, the spectra of the first and second sets of work spectra being made up of numerical data, the quality criterion is a criterion of representativity of data, which implements a metric characterizing a distance between the said sets.
According to another characteristic of the invention, the spectra of the first and second sets of work spectra being made up of numerical data, the quality criterion is a first criterion of homogeneity of the said data comparing on the one hand the shapes and on the other hand the orientations of the said sets.
According to another characteristic of the invention, the spectra of the first and second sets of work spectra being made up of numerical data, the quality criterion is a second criterion of homogeneity of the data intercomparing the densities of the said numerical data.
According to another characteristic of the invention, the quality criterion is a global criterion computed via a formula involving at least two criteria chosen from among the criterion of representativity, the first criterion of homogeneity and the second criterion of homogeneity.
According to another characteristic of the invention, in order to track the evolution over time of the quality criterion, a monovariate control chart is used.
According to another characteristic of the invention, in order to track the evolution over time of the quality criterion, a causes/effects diagram is used.